Polyurethanes are prepared by reacting an organic polyisocyanate with a polyol in the presence of additional components like catalysts, surfactants etc. When preparing polyurethane foams a foaming agent is usually added.
Carbohydrates are known as initiators in the production of polyether polyols or as direct additives to a polyol or blend of polyols as part of the polyurethane formulation. Simple carbohydrates such as sucrose, sorbitol, fructose and glucose have been used to initiate polyether polyols designed to facilitate solely water blown rigid foams as described in U.S. Pat. No. 5,690,855. U.S. Pat. No. 5,185,383 uses hexoses as a polyol starter and U.S. Pat. No. 4,943,597 describes a polyol composition wherein simple carbohydrates such as dextrose, sorbitol, sucrose, alpha-methylgucoside and alpha-hydroxyethylglucoside are suitable initiators for a high molecular weight, high functionality polyol which can be used to make substantially water-blown rigid foams.
More complex carbohydrate units such as cellulose and starches have also been employed in the production of polyurethanes as described in U.S. Pat. No. 4,520,139. Complex carbohydrate units such as pectins, starch or other amylaceous materials may be used in foaming systems with or without an auxiliary blowing agent. The starches may be modified prior to use. Thus in U.S. Pat. No. 4,401,772 methyl glucoside is formed by an acid catalyzed reaction with starch. This is then reacted with a suitable amine and an alkylene oxide to form a polyether polyol. More recently a jet-cooked starch oil composite has been used in conjunction with low molecular weight glycol polyol to make a polyurethane foam with altered characteristics, as described in R. L. Cunningham, et al. J Appl Polym Sci 69: 957, 1998. Unmodified cellulose and starches, and polysaccharides have also been converted to polyurethane precursors by alkoxylation and more specifically propoxylation. Formation of polyether polyols resulted in compounds useful as precursors for fat mimetics in U.S. Pat. No. 5,273,772, and in rigid and flexible polyurethanes foams in U.S. Pat. No. 4,585,858. In the process of U.S. Pat. No. 5,273,772, involving carbohydrates capable of having more complex, highly branched and random glucosidic linkages, water must be rigorously removed prior to alkoxylation. The composition of U.S. Pat. No. 4,585,858 can tolerate about 15–23% water when crude starch is one of the initiators, however the document specifically refers to starch-meaning compounds with 1,4 glucosidic linkages derived from any vegetable source with and without chemical modification.
The novel alkoxylated polyol composition specified by the current invention is differentiated from the prior art in that it is derived from a highly branched randomly bonded carbohydrate and may be alkoxylated in the presence of relatively high water content.
As direct additives untreated carbohydrates have been incorporated into polyurethane foams in two ways—1) as a partial or complete replacement for the polyol component, and 2) as an unreacted additive or filler. The carbohydrate can be introduced into the foam starting materials either as a solution or as a fine solid. When added as a solution, the hydroxyl groups on the carbohydrate can react with the isocyanate component and become chemically incorporated into the structure of the polyurethane. Examples of carbohydrates include certain starches, corn syrup, cellulose, pectin as described in U.S. Pat. No. 4,520,139, mono- and disaccharides as described in U.S. Pat. Nos. RE31,757, 4,400,475, 4,404,294, 4,417,998, oligosaccharides as described in U.S. Pat. No. 4,404,295 and pregelatinized starch as described in U.S. Pat. No. 4,197,372. As a solid dispersion, the carbohydrate may be inert in the polymerization reaction, but is physically incorporated into the foam. The advantage is lower cost and the ability of the carbohydrates to char upon combustion, preventing further burning and/or dripping of the foam and reducing smoke formation as described in U.S. Pat. Nos. 3,956,202, 4,237,182, 4,458,034, 4,520,139, 4,654,375. Starch and cellulose are commonly used for this purpose. The starch or cellulose may also be chemically modified prior to foam formulation as described in U.S. Pat. Nos. 3,956,202 and 4,458,034.
In US 20040014829 polyether polyols for foam applications are based upon at least a first initiator having an average functionality of greater than eight but advantageously less than 18. The first initiator may be made up of molecules of a single functionality greater than eight, alternatively it may comprise a plurality of species having functionalities different from each other. The highest nominal functionality mentioned in such a blend is 33. For example hydrogenated starch hydrolysates, which are formed by breaking the starch molecule into smaller oligomers at the ether bond between glucose rings, may be the first initiator of the application. A second initiator may be used, having lower functionality than the range of functionalities in the first initiator. The application does not mention any highly branched species.
A major issue facing the polyurethane foam industry has been and continues to be its dependence upon fluorocarbon blowing agents. By international agreement, the original Freon type chlorofluorocarbons (CFCs) have already been banned and production of the first round replacement, HCFC 141b was phased-out beginning in 2003. Non-ozone depleting, pentafluoropropane isomers (HFC 245), are currently in production. Eventually all HCFC and HFC production will be phased-out. As production with these blowing agents is phased-out, many formulators have investigated low boiling point hydrocarbons like pentane as alternatives. In addition, the cost of fluorinated blowing agents has risen dramatically, such that the blowing agents are much more expensive than the other major ingredients in foam formulations. Therefore foam formulations are being developed with water to minimize formulation costs.
Carbon dioxide generated by the reaction of water and isocyanate has long been recognized as the foaming mechanism in water-blown polyurethane foams. Since water reacts rapidly and exothermically with isocyanate, control of the reaction in water blown foams is critical. Ways of improving the use of water via catalyst selection have focused on amines as described in U.S. Pat. Nos. 5,162,286 and 6,232,356. However, in many other water-blown foams, water merely initiates foaming by a physical blowing agent vaporized by heat generated from the reaction of water with isocyanate. In other instances, typified by U.S. Pat. Nos. 5,690,855 and 5,686,500, a blend of amine and non amine-initiated polyether polyols was used to improve the predictability of the ensuing polyurethane reaction. An ingredient that will facilitate increased water usage without an auxiliary blowing agent would be of great merit to the industry.
It should be noted that all documents cited in this text (“herein cited documents”) as well as each document or reference cited in each of the herein-cited documents, and all manufacturer's literature, specifications, instructions, product data sheets, material data sheets, and the like, as to the product mentioned ii this text, are hereby expressly incorporated herein by reference.